Peptide fragments obtained by digestion of pure rabbit lung converting enzyme will be isolated and characterized structurally. Mouse monoclonal antienzyme antibodies will be prepared and their interactions with fragments of the enzyme, with the pure intact holoenzyme, with plasma membranes containing the enzyme, and with the enzyme in vivo will be examined. The structural difference between pure converting enzymes from the lung and testis will be identified and an attempt will be made to elucidate its biosynthetic basis.